The underframe of a railway freight car generally includes a longitudinally extending center sill with transverse body bolsters intersecting the center sill and outwardly extending therefrom. The transverse body bolsters are positioned near the ends of the car underframe above the area where the wheeled truck assemblies are located. The transverse body bolsters are attached to the center sill and apply a great loading force to the vertical sidewalls of the center sill. In order to prevent the collapse of the center sill walls due to this loading a center filler is secured within the center sill in the area adjacent the body bolster. A center plate is also secured to the underframe, beneath the center filler, which makes pivotal engagement with a mating center bowl on the bolster of the wheeled truck assembly.
Heretofore, it has been common to combine the center filler and center brace into a unitary cast structure. While this unitary casting approach provides a structurally strong center filler, it has several inherent shortcomings. The integral center filler, center plate castings are naturally costly to manufacture due to the extensive coring required and the resultant structures are also quite heavy. Further, due to the dynamic loading conditions present during use, the center plates become worn or cracked and must be replaced periodically. In the integral cast structures, the entire unit must be removed from the center sill in order to replace the center plate, even though the center filler may be in workable condition.
In order to overcome the shortcomings of the integral cast structures, separate center filler and center plate constructions have come into usage in the art. In these constructions, the center filler is generally cast and has a cast or forged center plate, welded, bolted or riveted, either directly or indirectly thereto. Other variations have also been suggested involving cast-weld center filler, center plate constructions. Examples of these various prior art proposals are set forth in U.S. Pat. Nos. 2,003,341; 2,078,176; 2,995,258; 3,670,662; 3,770,139; and 3,797,674.
While the separate center filler, center plate proposls of the prior art have provided the desired feature of easy removal and replacement of the center plate bowl, these structures still have inherent shortcomings. A well braced, cast, center filler is expensive to manufacture due to the intricate coring required in the molding process and such structures are, likewise, correspondingly heavy. Less expensive castings require less coring but these do not provide proper rigidity and stress distribution in the center filler structure. In the typical underframe assembly, the top edges of the center filler casting contact the top wall of the center sill and the center plate is riveted to the bottom of the center filler and riveted to the body bolster by way of its extended tie plate. The variations in dimensional tolerances in the depth of the center sill and height of the cast center filler often results in a poor fit-up between the center filler and center plate due to the fact that the center filler may not be flush with the lower flanges of the center sill. This poor fit-up causes the center plate to flex until it receives back up from the center filler by which event there results an overstressed condition at the juncture of the center plate and its tie plate. This problem, sometimes, referred to as "tin-canning" in the art, caused by a poorly backed up center plate, has heretofore caused the early and chronic failure of the center plate.
The railway industry standards have recently required in certain instances that the bottom of the center filler and the center sill flanges be machined flat after installation so that flush surfaces result. These same standards also require the flat machining of the center plate and tie plate in order to assure a face-to-face fit in order to eliminate the tine-canning problem. It is, of course, appreciated that this required machining operation is costly in that it is time consuming and requires special machinery.
The invention disclosed and claimed herein solves many of the problems heretofore encountered in the design and construction of center filler, center plate structures.